Cache block budgeting techniques

ABSTRACT

Methods, systems, and devices for cache block budgeting techniques are described. In some memory systems, a controller may configure a memory device with a cache. The cache may include a first subset of blocks configured to statically operate in a first mode and a second subset of blocks configured to dynamically switch between operating in the first mode and a second mode. A block operating in the second mode may be configured to store relatively more bits per memory cell than a block operating in the first mode. The controller may track and store, for each block of the second subset of blocks, a respective ratio of cycles performed in the first mode to cycles performed in the second mode. The controller may select a block from the second subset of blocks to switch between modes responsive to a trigger and based on the respective ratio for the block.

FIELD OF TECHNOLOGY

The following relates generally to one or more systems for memory andmore specifically to cache block budgeting techniques.

BACKGROUND

Memory devices are widely used to store information in variouselectronic devices such as computers, user devices, cameras, digitaldisplays, and the like. Information is stored by programing memory cellswithin a memory device to various states. For example, binary memorycells may be programmed to one of two supported states, oftencorresponding to a logic 1 or a logic 0. In some examples, a singlememory cell may support more than two possible states, any one of whichmay be stored by the memory cell. To access information stored by amemory device, a component may read, or sense, the state of one or morememory cells within the memory device. To store information, a componentmay write, or program, one or more memory cells within the memory deviceto corresponding states.

Various types of memory devices exist, including magnetic hard disks,random access memory (RAM), read-only memory (ROM), dynamic RAM (DRAM),synchronous dynamic RAM (SDRAM), static RAM (SRAM), ferroelectric RAM(FeRAM), magnetic RAM (MRAM), resistive RAM (RRAM), flash memory, phasechange memory (PCM), 3-dimensional cross-point memory (3D cross point),not-or (NOR) and not-and (NAND) memory devices, and others. Memorydevices may be volatile or non-volatile. Volatile memory cells (e.g.,DRAM cells) may lose their programmed states over time unless they areperiodically refreshed by an external power source. Non-volatile memorycells (e.g., NAND memory cells) may maintain their programmed states forextended periods of time even in the absence of an external powersource.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an example of a system that supports cache blockbudgeting techniques in accordance with examples as disclosed herein.

FIG. 2 illustrates an example of a system that supports cache blockbudgeting techniques in accordance with examples as disclosed herein.

FIG. 3 illustrates an example of a memory system that supports cacheblock budgeting techniques in accordance with examples as disclosedherein.

FIG. 4 illustrates an example of a flow diagram that supports cacheblock budgeting techniques in accordance with examples as disclosedherein.

FIG. 5 shows a block diagram of a memory system that supports cacheblock budgeting techniques in accordance with examples as disclosedherein.

FIG. 6 shows a flowchart illustrating a method or methods that supportcache block budgeting techniques in accordance with examples asdisclosed herein.

DETAILED DESCRIPTION

Some memory devices, such as NAND memory, may include a cache thatincludes subsets of memory cells (e.g., in a memory array) for storingdata or other information. In some examples, the cache may includeblocks of memory that may support fewer bits per cell than other blocksin the memory device. For example, the cache may include one or moresingle level cell (SLC) blocks, which may include relatively fewer bitsper cell than other blocks, such as blocks including multi-level cells(MLC), triple-level cells (TLC), quad-level cells (QLC), penta-levelcells (PLC), etc., or any combination of these or other multiple-levelmemory cells. Such a cache may improve endurance and performance of thememory device due to the improved performance of the blocks that supportfewer bits per cell (e.g., relatively higher reliability, relativelyfaster access operations, relatively greater endurance) as compared tothe other blocks for data storage. In some cases, however, the cache maybe associated with reduced capacity for the memory device (e.g., due tostoring fewer bits per cell than blocks outside the cache), which mayresult in decreased memory device storage capacity and performance forsome operations such as wear leveling, garbage collection, or the like(e.g., operations that may benefit from an overprovisioning pool ofblocks or resources to be used).

As described herein, the cache may include a subset of dynamic blocksthat may be able to switch between a first mode that supports relativelyfewer bits per cell (e.g., SLC, MLC, TLC) and a second mode thatsupports relatively more bits per cell (e.g., MLC, TLC, or QLC). In someexamples, a program and erase (P/E) cycle performed on a dynamic blockin the second mode may wear the block more than a P/E cycle in the firstmode (e.g., due to the greater quantity of bits per cell correspondingto the second mode). A memory system controller may configure the cacheto support a target total bytes written (TBW) in accordance with atarget capacity for the memory device. The memory system controller mayconfigure, for at least some if not each dynamic block in the cache andin accordance with the target TBW for the cache, a target ratio betweencycles performed in the first mode and cycles performed in the secondmode. The target ratio may correspond to a first target cycle count forthe first mode and a second target cycle count for the second mode insome examples. As the memory device is used (e.g., during productruntime), the memory system controller may track the cycle counts foreach dynamic block in the cache. If the memory system controlleridentifies a trigger to select one or more dynamic blocks to switch fromthe first mode to the second mode (or from the second mode to the firstmode), the memory system controller may select the one or more dynamicblocks based on or in response to the cycle counts, a target cyclingratio for the respective blocks, or both. The trigger may be, forexample, a capacity of the memory device satisfying (e.g., exceeding orbeing equal to) or falling below a target capacity of the memory device,a write command for the cache, an erase command for the cache, or anycombination thereof.

Additionally or alternatively, the memory system controller may beconfigured to modify a target cycling ratio for one or more dynamicblocks based on or in response to a level of usage of the cache (e.g.,by a host system). During runtime, the memory system controller mayperiodically compare a TBW to the cache with the target TBW for thecache. If the actual TBW is different from the target TBW (e.g., for aspecific time period), the memory system controller may determine toadjust (e.g., increase or decrease) the target cycling ratio for one ormore dynamic blocks. As such, the memory system controller may utilizeone or more processes to improve allocation of blocks within a cache,which may improve performance and endurance of a memory device whilemaintaining capacity targets for the memory device.

Features of the disclosure are initially described in the context ofsystems and devices with reference to FIGS. 1 and 2 . Features of thedisclosure are described in the context of memory systems and processflows with reference to FIGS. 3 and 4 . These and other features of thedisclosure are further illustrated by and described in the context of anapparatus diagram and flowchart that relate to cache block budgetingtechniques with reference to FIGS. 5 and 6 .

FIG. 1 illustrates an example of a system 100 that supports cache blockbudgeting techniques in accordance with examples as disclosed herein.The system 100 includes a host system 105 coupled with a memory system110.

A memory system 110 may be or include any device or collection ofdevices, where the device or collection of devices includes at least onememory array. For example, a memory system 110 may be or include aUniversal Flash Storage (UFS) device, an embedded Multi-Media Controller(eMMC) device, a flash device, a universal serial bus (USB) flashdevice, a secure digital (SD) card, a solid-state drive (SSD), a harddisk drive (HDD), a dual in-line memory module (DIMM), a small outlineDIMM (SO-DIMM), or a non-volatile DIMM (NVDIMM), among otherpossibilities.

The system 100 may be included in a computing device such as a desktopcomputer, a laptop computer, a network server, a mobile device, avehicle (e.g., airplane, drone, train, automobile, or other conveyance),an Internet of Things (IoT) enabled device, an embedded computer (e.g.,one included in a vehicle, industrial equipment, or a networkedcommercial device), or any other computing device that includes memoryand a processing device.

The system 100 may include a host system 105, which may be coupled withthe memory system 110. In some examples, this coupling may include aninterface with a host system controller 106, which may be an example ofa controller or control component configured to cause the host system105 to perform various operations in accordance with examples asdescribed herein. The host system 105 may include one or more devices,and in some cases may include a processor chipset and a software stackexecuted by the processor chipset. For example, the host system 105 mayinclude an application configured for communicating with the memorysystem 110 or a device therein. The processor chipset may include one ormore cores, one or more caches (e.g., memory local to or included in thehost system 105), a memory controller (e.g., NVDIMM controller), and astorage protocol controller (e.g., peripheral component interconnectexpress (PCIe) controller, serial advanced technology attachment (SATA)controller). The host system 105 may use the memory system 110, forexample, to write data to the memory system 110 and read data from thememory system 110. Although one memory system 110 is shown in FIG. 1 ,the host system 105 may be coupled with any quantity of memory systems110.

The host system 105 may be coupled with the memory system 110 via atleast one physical host interface. The host system 105 and the memorysystem 110 may in some cases be configured to communicate via a physicalhost interface using an associated protocol (e.g., to exchange orotherwise communicate control, address, data, and other signals betweenthe memory system 110 and the host system 105). Examples of a physicalhost interface may include, but are not limited to, a SATA interface, aUFS interface, an eMMC interface, a PCIe interface, a USB interface, aFiber Channel interface, a Small Computer System Interface (SCSI), aSerial Attached SCSI (SAS), a Double Data Rate (DDR) interface, a DIMMinterface (e.g., DIMM socket interface that supports DDR), an Opennot-and (NAND) Flash Interface (ONFI), and a Low Power Double Data Rate(LPDDR) interface. In some examples, one or more such interfaces may beincluded in or otherwise supported between a host system controller 106of the host system 105 and a memory system controller 115 of the memorysystem 110. In some examples, the host system 105 may be coupled withthe memory system 110 (e.g., the host system controller 106 may becoupled with the memory system controller 115) via a respective physicalhost interface for each memory device 130 included in the memory system110, or via a respective physical host interface for each type of memorydevice 130 included in the memory system 110.

The memory system 110 may include a memory system controller 115 and oneor more memory devices 130. A memory device 130 may include one or morememory arrays of any type of memory cells (e.g., non-volatile memorycells, volatile memory cells, or any combination thereof). Although twomemory devices 130-a and 130-b are shown in the example of FIG. 1 , thememory system 110 may include any quantity of memory devices 130.Further, if the memory system 110 includes more than one memory device130, different memory devices 130 within the memory system 110 mayinclude the same or different types of memory cells.

The memory system controller 115 may be coupled with and communicatewith the host system 105 (e.g., via the physical host interface) and maybe an example of a controller or control component configured to causethe memory system 110 to perform various operations in accordance withexamples as described herein. The memory system controller 115 may alsobe coupled with and communicate with memory devices 130 to performoperations such as reading data, writing data, erasing data, orrefreshing data at a memory device 130—among other such operations—whichmay generically be referred to as access operations. In some cases, thememory system controller 115 may receive commands from the host system105 and communicate with one or more memory devices 130 to execute suchcommands (e.g., at memory arrays within the one or more memory devices130). For example, the memory system controller 115 may receive commandsor operations from the host system 105 and may convert the commands oroperations into instructions or appropriate commands to achieve thedesired access of the memory devices 130. In some cases, the memorysystem controller 115 may exchange data with the host system 105 andwith one or more memory devices 130 (e.g., in response to or otherwisein association with commands from the host system 105). For example, thememory system controller 115 may convert responses (e.g., data packetsor other signals) associated with the memory devices 130 intocorresponding signals for the host system 105.

The memory system controller 115 may be configured for other operationsassociated with the memory devices 130. For example, the memory systemcontroller 115 may execute or manage operations such as wear-levelingoperations, garbage collection operations, error control operations suchas error-detecting operations or error-correcting operations, encryptionoperations, caching operations, media management operations, backgroundrefresh, health monitoring, and address translations between logicaladdresses (e.g., logical block addresses (LBAs)) associated withcommands from the host system 105 and physical addresses (e.g., physicalblock addresses) associated with memory cells within the memory devices130.

The memory system controller 115 may include hardware such as one ormore integrated circuits or discrete components, a buffer memory, or acombination thereof. The hardware may include circuitry with dedicated(e.g., hard-coded) logic to perform the operations ascribed herein tothe memory system controller 115. The memory system controller 115 maybe or include a microcontroller, special purpose logic circuitry (e.g.,a field programmable gate array (FPGA), an application specificintegrated circuit (ASIC), a digital signal processor (DSP)), or anyother suitable processor or processing circuitry.

The memory system controller 115 may also include a local memory 120. Insome cases, the local memory 120 may include read-only memory (ROM) orother memory that may store operating code (e.g., executableinstructions) executable by the memory system controller 115 to performfunctions ascribed herein to the memory system controller 115. In somecases, the local memory 120 may additionally or alternatively includestatic random access memory (SRAM) or other memory that may be used bythe memory system controller 115 for internal storage or calculations,for example, related to the functions ascribed herein to the memorysystem controller 115. Additionally or alternatively, the local memory120 may serve as a cache for the memory system controller 115. Forexample, data may be stored in the local memory 120 if read from orwritten to a memory device 130, and the data may be available within thelocal memory 120 for subsequent retrieval for or manipulation (e.g.,updating) by the host system 105 (e.g., with reduced latency relative toa memory device 130) in accordance with a cache policy.

Although the example of the memory system 110 in FIG. 1 has beenillustrated as including the memory system controller 115, in somecases, a memory system 110 may not include a memory system controller115. For example, the memory system 110 may additionally oralternatively rely upon an external controller (e.g., implemented by thehost system 105) or one or more local controllers 135, which may beinternal to memory devices 130, respectively, to perform the functionsascribed herein to the memory system controller 115. In general, one ormore functions ascribed herein to the memory system controller 115 mayin some cases instead be performed by the host system 105, a localcontroller 135, or any combination thereof. In some cases, a memorydevice 130 that is managed at least in part by a memory systemcontroller 115 may be referred to as a managed memory device. An exampleof a managed memory device is a managed NAND (MNAND) device.

A memory device 130 may include one or more arrays of non-volatilememory cells. For example, a memory device 130 may include NAND (e.g.,NAND flash) memory, ROM, phase change memory (PCM), self-selectingmemory, other chalcogenide-based memories, ferroelectric random accessmemory (RAM) (FeRAM), magneto RAM (MRAM), NOR (e.g., NOR flash) memory,Spin Transfer Torque (STT)-MRAM, conductive bridging RAM (CBRAM),resistive random access memory (RRAM), oxide based RRAM (OxRAM),electrically erasable programmable ROM (EEPROM), or any combinationthereof. Additionally or alternatively, a memory device 130 may includeone or more arrays of volatile memory cells. For example, a memorydevice 130 may include RAM memory cells, such as dynamic RAM (DRAM)memory cells and synchronous DRAM (SDRAM) memory cells.

In some examples, a memory device 130 may include (e.g., on a same dieor within a same package) a local controller 135, which may executeoperations on one or more memory cells of the respective memory device130. A local controller 135 may operate in conjunction with a memorysystem controller 115 or may perform one or more functions ascribedherein to the memory system controller 115. For example, as illustratedin FIG. 1 , a memory device 130-a may include a local controller 135-aand a memory device 130-b may include a local controller 135-b.

In some cases, a memory device 130 may be or include a NAND device(e.g., NAND flash device). A memory device 130 may be or include amemory die 160. For example, in some cases, a memory device 130 may be apackage that includes one or more dies 160. A die 160 may, in someexamples, be a piece of electronics-grade semiconductor cut from a wafer(e.g., a silicon die cut from a silicon wafer). Each die 160 may includeone or more planes 165, and each plane 165 may include a respective setof blocks 170, where each block 170 may include a respective set ofpages 175, and each page 175 may include a set of memory cells.

In some cases, a NAND memory device 130 may include memory cellsconfigured to each store one bit of information, which may be referredto as SLCs. Additionally or alternatively, a NAND memory device 130 mayinclude memory cells configured to each store multiple bits ofinformation, which may be referred to as MLCs if configured to eachstore two bits of information, as TLCs if configured to each store threebits of information, as QLCs if configured to each store four bits ofinformation, or more generically as multiple-level memory cells.Multiple-level memory cells may provide greater density of storage(e.g., increased capacity) relative to SLC memory but may, in somecases, involve narrower read or write margins or greater complexitiesfor supporting circuitry. In some examples, SLC memory may be associatedwith higher reliability, faster access operations, improved endurance,and the like, than multiple-level memory cells.

Some memory devices 130 may include static SLC memory cells, which mayoperate in an SLC mode throughout a lifetime of the memory device 130.Static SLC memory cells may support relatively high reliability andendurance for the memory device 130, but may be associated with a lowerdensity of storage than other memory cells. As a quantity of datawritten to the memory device 130 (e.g., a level of usage of the memorydevice 130) increases, the capacity of the memory device 130 maydecrease (e.g., an over-provisioning pool that includes available memorycells within the memory device 130 may decrease). As such, a memorydevice 130 that includes a relatively large quantity of static SLCmemory cells may store a relatively low quantity of data (e.g., a lowcapacity). To maintain sufficient capacity within a memory device 130while improving endurance and performance, a memory device 130 mayinclude one or more dynamic memory cells. The one or more dynamic memorycells may be programmed as SLC memory cells or multiple-level memorycells (e.g., MLC, TLC, QLC, PLC, etc.).

In some cases, planes 165 may refer to groups of blocks 170, and in somecases, concurrent operations may take place within different planes 165.For example, concurrent operations may be performed on memory cellswithin different blocks 170 so long as the different blocks 170 are indifferent planes 165. In some cases, performing concurrent operations indifferent planes 165 may be subject to one or more restrictions, such asidentical operations being performed on memory cells within differentpages 175 that have the same page address within their respective planes165 (e.g., related to command decoding, page address decoding circuitry,or other circuitry being shared across planes 165).

In some cases, a block 170 may include memory cells organized into rows(pages 175) and columns (e.g., strings, not shown). For example, memorycells in a same page 175 may share (e.g., be coupled with) a common wordline, and memory cells in a same string may share (e.g., be coupledwith) a common digit line (which may alternatively be referred to as abit line).

For some NAND architectures, memory cells may be read and programmed(e.g., written) at a first level of granularity (e.g., at the page levelof granularity) but may be erased at a second level of granularity(e.g., at the block level of granularity). That is, a page 175 may bethe smallest unit of memory (e.g., set of memory cells) that may beindependently programmed or read (e.g., programed or read concurrentlyas part of a single program or read operation), and a block 170 may bethe smallest unit of memory (e.g., set of memory cells) that may beindependently erased (e.g., erased concurrently as part of a singleerase operation). Further, in some cases, NAND memory cells may beerased before they can be re-written with new data. Thus, for example, aused page 175 may in some cases not be updated until the entire block170 that includes the page 175 has been erased.

In some cases, to update some data within a block 170 while retainingother data within the block 170, the memory device 130 may copy the datato be retained to a new block 170 and write the updated data to one ormore remaining pages of the new block 170. The memory device 130 (e.g.,the local controller 135) or the memory system controller 115 may markor otherwise designate the data that remains in the old block 170 asinvalid or obsolete and may update a logical-to-physical (L2P) mappingtable to associate the logical address (e.g., LBA) for the data with thenew, valid block 170 rather than the old, invalid block 170. In somecases, such copying and remapping may be performed instead of erasingand rewriting the entire old block 170 due to latency or wearoutconsiderations, for example. In some cases, one or more copies of an L2Pmapping table may be stored within the memory cells of the memory device130 (e.g., within one or more blocks 170 or planes 165) for use (e.g.,reference and updating) by the local controller 135 or memory systemcontroller 115.

In some cases, L2P mapping tables may be maintained and data may bemarked as valid or invalid at the page level of granularity, and a page175 may contain valid data, invalid data, or no data. Invalid data maybe data that is outdated due to a more recent or updated version of thedata being stored in a different page 175 of the memory device 130.Invalid data may have been previously programmed to the invalid page 175but may no longer be associated with a valid logical address, such as alogical address referenced by the host system 105. Valid data may be themost recent version of such data being stored on the memory device 130.A page 175 that includes no data may be a page 175 that has never beenwritten to or that has been erased.

In some cases, a memory system controller 115 or a local controller 135may perform operations (e.g., as part of one or more media managementalgorithms) for a memory device 130, such as wear leveling, backgroundrefresh, garbage collection, scrub, block scans, health monitoring, orothers, or any combination thereof. For example, within a memory device130, a block 170 may have some pages 175 containing valid data and somepages 175 containing invalid data. To avoid waiting for all of the pages175 in the block 170 to have invalid data in order to erase and reusethe block 170, an algorithm referred to as “garbage collection” may beinvoked to allow the block 170 to be erased and released as a free blockfor subsequent write operations. Garbage collection may refer to a setof media management operations that include, for example, selecting ablock 170 that contains valid and invalid data, selecting pages 175 inthe block that contain valid data, copying the valid data from theselected pages 175 to new locations (e.g., free pages 175 in anotherblock 170), marking the data in the previously selected pages 175 asinvalid, and erasing the selected block 170. As a result, the quantityof blocks 170 that have been erased may be increased such that moreblocks 170 are available to store subsequent data (e.g., datasubsequently received from the host system 105). In some examples,performance of a memory device 130 during garbage collection and wearleveling operations may be referred to as dirty performance.

In some examples, an overprovisioning pool within the memory device 130may include the free blocks 170 (e.g., blocks 170 that are not currentlystoring data) that are erased during such operations, which may improveefficiency and reliability of the media management operations for thememory device 130. As a level of usage of the memory device 130increases, a capacity of available blocks within the memory device 130(e.g., and a corresponding capacity of the overprovisioning pool) maydecrease, which may result in reduced performance (e.g., dirtyperformance). In some examples, a memory device 130 may include a cachethat includes blocks 170 that support a first mode of operation (e.g.,SLC memory). The first mode may support fewer bits per memory cell thana second mode (e.g., multiple-level cell memory) and may be associatedwith reduced capacity. As such, if a memory device 130 includes a cacheof blocks that operate in the first mode, a capacity of the device maybe reduced, which may result in reduced overprovisioning and reducedperformance of the memory device 130.

A cache within a memory device 130 as described herein may be configuredto include a first subset of blocks that are configured to operate inthe first mode and a second subset of blocks that are configured todynamically switch between operating in the first mode and the secondmode, which may be referred to as dynamic blocks. The memory systemcontroller 115 may configure the cache to support a target TBW based onor in response to a target capacity for the memory device 130. Thememory system controller 115 may configure, for each dynamic block inthe cache, a target cycle ratio associated with a first target cyclecount for the first mode and a second target cycle count for the secondmode in accordance with the target TBW (e.g., a total target TBW) forthe cache. In some examples, a P/E cycle performed on a block in thesecond mode may wear a block more than a P/E cycle performed on theblock in the first mode, and the target cycling ratio may be calculatedaccording to a ratio of wear in the first mode to wear in the secondmode to maintain sufficient endurance for each block 170.

As the memory device 130 is used by a host system 105, the memory systemcontroller 115 may track the cycle counts for each dynamic block in thecache. If the memory system controller 115 identifies a trigger toselect one or more dynamic blocks to switch from the first mode to thesecond mode or from the second mode to the first mode, the memory systemcontroller 115 may select the one or more dynamic blocks based on or inresponse to the cycle counts and a target cycling ratio for therespective dynamic blocks. The trigger may be, for example, a capacityof the memory device 130 exceeding or falling below a target capacity ofthe memory device 130, a write command for the cache, an erase commandfor the cache, or any combination thereof. The memory system controller115 may additionally or alternatively modify the target cycle ratios forone or more dynamic blocks in accordance with a level of usage of thecache. The memory system controller 115 may periodically compare anactual TBW with the target TBW for the cache. If the actual TBW isdifferent from the target TBW (e.g., for a specific time period, at aspecific reference time), the memory system controller 115 may determineto adjust (e.g., increase or decrease) the target cycling ratio for oneor more dynamic blocks. As such, the memory system controller 115 mayutilize one or more processes to improve allocation of dynamic blockswithin a cache, which may improve performance and endurance of a memorydevice 130 while maintaining a capacity target for the memory device130.

The system 100 may include any quantity of non-transitory computerreadable media that support cache block budgeting techniques. Forexample, the host system 105, the memory system controller 115, or amemory device 130 may include or otherwise may access one or morenon-transitory computer readable media storing instructions (e.g.,firmware) for performing the functions ascribed herein to the hostsystem 105, memory system controller 115, or memory device 130. Forexample, such instructions, if executed by the host system 105 (e.g., bythe host system controller 106), by the memory system controller 115, orby a memory device 130 (e.g., by a local controller 135), may cause thehost system 105, memory system controller 115, or memory device 130 toperform one or more associated functions as described herein.

In some cases, a memory system 110 may utilize a memory systemcontroller 115 to provide a managed memory system that may include, forexample, one or more memory arrays and related circuitry combined with alocal (e.g., on-die or in-package) controller (e.g., local controller135). An example of a managed memory system is a managed NAND (MNAND)system.

FIG. 2 illustrates an example of a system 200 that supports cache blockbudgeting techniques in accordance with examples as disclosed herein.The system 200 may be an example of a system 100 as described withreference to FIG. 1 or aspects thereof. The system 200 may include amemory system 210 configured to store data received from the host system205 and to send data to the host system 205, if requested by the hostsystem 205 using access commands (e.g., read commands or writecommands). The system 200 may implement aspects of the system 100 asdescribed with reference to FIG. 1 . For example, the memory system 210and the host system 205 may be examples of the memory system 110 and thehost system 105, respectively.

The memory system 210 may include one or more memory devices 240 tostore data transferred between the memory system 210 and the host system205, e.g., in response to receiving access commands from the host system205, as described herein. The one or more memory devices 240 mayexamples of the memory devices as described with reference to FIG. 1 .For example, the memory devices 240 may include NAND memory, PCM,self-selecting memory, 3D cross point, other chalcogenide-basedmemories, FERAM, MRAM, NOR (e.g., NOR flash) memory, STT-MRAM, CBRAM,RRAM, or OxRAM.

The memory system 210 may include a storage controller 230 forcontrolling the passing of data directly to and from a memory device240, e.g., for storing data, retrieving data, and determining memorylocations in which to store data and from which to retrieve data. Thestorage controller 230 may communicate with the one or more memorydevices 240 directly or via a bus (not shown) using a protocol specificto each type of memory device 240. In some cases, a single storagecontroller 230 may be used to control multiple memory devices 240 of thesame or different types. In some cases, the memory system 210 mayinclude multiple storage controllers 230, e.g., a different storagecontroller 230 for each type of memory device 240. In some cases, astorage controller 230 may implement aspects of a local controller 135as described with reference to FIG. 1 .

The memory system 210 may additionally include an interface 220 forcommunication with the host system 205 and a buffer 225 for temporarystorage of data being transferred between the host system 205 and thememory device 240. The interface 220, buffer 225, and storage controller230 may be for translating data between the host system 205 and thememory device 240, e.g., as shown by a data path 250, and may becollectively referred to as data path components.

Using the buffer 225 to temporarily store data during transfers mayallow data to be buffered as commands are being processed, therebyreducing latency between commands and allowing arbitrary data sizesassociated with commands. This may also allow bursts of commands to behandled, and the buffered data may be stored or transmitted (or both)once a burst has stopped. The buffer 225 may include relatively fastmemory (e.g., some types of volatile memory, such as SRAM or DRAM) orhardware accelerators or both to allow fast storage and retrieval ofdata to and from the buffer 225. The buffer 225 may include data pathswitching components for bi-directional data transfer between the buffer225 and other components.

The temporary storage of data within a buffer 225 may refer to thestorage of data in the buffer 225 during the execution of accesscommands. That is, upon completion of an access command, the associateddata may no longer be maintained in the buffer 225 (e.g., may beoverwritten with data for additional access commands). In addition, thebuffer 225 may be a non-cache buffer. That is, data may not be readdirectly from the buffer 225 by the host system 205. For example, readcommands may be added to a queue without an operation to match theaddress to addresses already in the buffer 225 (e.g., without a cacheaddress match or lookup operation).

The memory system 210 may additionally include a memory systemcontroller 215 for executing the commands received from the host system205 and controlling the data path components in the moving of the data.The memory system controller 215 may be an example of the memory systemcontroller 115 as described with reference to FIG. 1 . A bus 235 may beused to communicate between the system components. In some examples, thememory system controller 215 may be an example of a processor associatedwith an ASIC. For example, the system 200 may include multiple memorydies. A first memory die (e.g., an ASIC controller die) may include theinterface 220, the buffer 225, the storage controller 230, or acombination thereof and may be controlled by the memory systemcontroller 215. In some cases, the first memory die may additionallyinclude the memory system controller 215. A second memory die mayinclude one or more memory devices 240 and may include a localcontroller (not shown). The memory dies may communicate with each otherusing the bus 235.

In some cases, one or more queues (e.g., a command queue 260, a bufferqueue 265, and a storage queue 270) may be used to control theprocessing of the access commands and the movement of the correspondingdata. This may be beneficial, e.g., if more than one access command fromthe host system 205 is processed concurrently by the memory system 210.The command queue 260, buffer queue 265, and storage queue 270 aredepicted at the interface 220, memory system controller 215, and storagecontroller 230, respectively, as examples of a possible implementation.However, queues, if used, may be positioned anywhere within the memorysystem 210.

Data transferred between the host system 205 and the one or more memorydevices 240 may take a different path in the memory system 210 thannon-data information (e.g., commands, status information). For example,the system components in the memory system 210 may communicate with eachother using a bus 235, while the data may use the data path 250 throughthe data path components instead of the bus 235. The memory systemcontroller 215 may control how and if data is transferred between thehost system 205 and the memory devices 240 by communicating with thedata path components over the bus 235 (e.g., using a protocol specificto the memory system 210).

If a host system 205 transmits access commands to the memory system 210,the commands may be received by the interface 220, e.g., according to aprotocol (e.g., a UFS protocol or an eMMC protocol). Thus, the interface220 may be considered a front end of the memory system 210. Upon receiptof each access command, the interface 220 may communicate the command tothe memory system controller 215, e.g., via the bus 235. In some cases,each command may be added to a command queue 260 by the interface 220 tocommunicate the command to the memory system controller 215.

The memory system controller 215 may determine whether an access commandhas been received based on or in response to the communication from theinterface 220. In some cases, the memory system controller 215 maydetermine the access command has been received by retrieving the commandfrom the command queue 260. The command may be removed from the commandqueue 260 after it has been retrieved therefrom, e.g., by the memorysystem controller 215. In some cases, the memory system controller 215may cause the interface 220, e.g., via the bus 235, to remove thecommand from the command queue 260.

Upon the determination that an access command has been received, thememory system controller 215 may execute the access command. For a readcommand, this may mean obtaining data from the memory devices 240 andtransmitting the data to the host system 205. For a write command, thismay mean receiving data from the host system 205 and moving the data toa memory device 240.

In either case, the memory system controller 215 may use the buffer 225for, among other things, temporary storage of the data being receivedfrom or sent to the host system 205. The buffer 225 may be considered amiddle end of the memory system 210. In some cases, buffer addressmanagement (e.g., pointers to address locations in the buffer 225) maybe performed by hardware (e.g., dedicated circuits) in the interface220, buffer 225, or storage controller 230.

To process a write command received from the host system 205, the memorysystem controller 215 may first determine if the buffer 225 hassufficient available space to store the data associated with thecommand. For example, the memory system controller 215 may determine,e.g., via firmware (e.g., controller firmware), an amount of spacewithin the buffer 225 that may be available to store data associatedwith the write command.

In some cases, a buffer queue 265 may be used to control a flow ofcommands associated with data stored in the buffer 225, including writecommands. The buffer queue 265 may include the access commandsassociated with data currently stored in the buffer 225. In some cases,the commands in the command queue 260 may be moved to the buffer queue265 by the memory system controller 215 and may remain in the bufferqueue 265 while the associated data is stored in the buffer 225. In somecases, each command in the buffer queue 265 may be associated with anaddress at the buffer 225. That is, pointers may be maintained thatindicate where in the buffer 225 the data associated with each commandis stored. Using the buffer queue 265, multiple access commands may bereceived sequentially from the host system 205 and at least portions ofthe access commands may be processed concurrently.

If the buffer 225 has sufficient space to store the write data, thememory system controller 215 may cause the interface 220 to transmit anindication of availability to the host system 205 (e.g., a “ready totransfer” indication), e.g., according to a protocol (e.g., a UFSprotocol or an eMMC protocol). As the interface 220 subsequentlyreceives from the host system 205 the data associated with the writecommand, the interface 220 may transfer the data to the buffer 225 fortemporary storage using the data path 250. In some cases, the interface220 may obtain from the buffer 225 or buffer queue 265 the locationwithin the buffer 225 to store the data. The interface 220 may indicateto the memory system controller 215, e.g., via the bus 235, if the datatransfer to the buffer 225 has been completed.

Once the write data has been stored in the buffer 225 by the interface220, the data may be transferred out of the buffer 225 and stored in amemory device 240. This may be done using the storage controller 230.For example, the memory system controller 215 may cause the storagecontroller 230 to retrieve the data out of the buffer 225 using the datapath 250 and transfer the data to a memory device 240. The storagecontroller 230 may be considered a back end of the memory system 210.The storage controller 230 may indicate to the memory system controller215, e.g., via the bus 235, that the data transfer to the memory device240 has been completed.

In some cases, a storage queue 270 may be used to aid with the transferof write data. For example, the memory system controller 215 may push(e.g., via the bus 235) write commands from the buffer queue 265 to thestorage queue 270 for processing. The storage queue 270 may includeentries for each access command. In some examples, the storage queue 270may additionally include a buffer pointer (e.g., an address) that mayindicate where in the buffer 225 the data associated with the command isstored and a storage pointer (e.g., an address) that may indicate thelocation in the one or more memory devices 240 associated with the data.In some cases, the storage controller 230 may obtain from the buffer225, buffer queue 265, or storage queue 270 the location within thebuffer 225 from which to obtain the data. The storage controller 230 maymanage the locations within the memory devices 240 to store the data(e.g., performing wear-leveling, garbage collection, and the like). Theentries may be added to the storage queue 270, e.g., by the memorysystem controller 215. The entries may be removed from the storage queue270, e.g., by the storage controller 230 or memory system controller 215upon completion of the transfer of the data.

To process a read command received from the host system 205, the memorysystem controller 215 may again first determine if the buffer 225 hassufficient available space to store the data associated with thecommand. For example, the memory system controller 215 may determine,e.g., via firmware (e.g., controller firmware), an amount of spacewithin the buffer 225 that may be available to store data associatedwith the read command.

In some cases, the buffer queue 265 may be used to aid with bufferstorage of data associated with read commands in a similar manner asdiscussed above with respect to write commands. For example, if thebuffer 225 has sufficient space to store the read data, the memorysystem controller 215 may cause the storage controller 230 to retrievethe data associated with the read command from a memory device 240 andstore the data in the buffer 225 for temporary storage using the datapath 250. The storage controller 230 may indicate to the memory systemcontroller 215, e.g., using the bus 235, that the data transfer to thebuffer 225 has been completed.

In some cases, the storage queue 270 may be used to aid with thetransfer of read data. For example, the memory system controller 215 maypush the read command to the storage queue 270 for processing. In somecases, the storage controller 230 may obtain from the buffer 225 orstorage queue 270 the location within the memory devices 240 from whichto retrieve the data. In some cases, the storage controller 230 mayobtain from the buffer queue 265 the location within the buffer 225 tostore the data. In some cases, the storage controller 230 may obtainfrom the storage queue 270 the location within the buffer 225 to storethe data. In some cases, the memory system controller 215 may move thecommand processed by the storage queue 270 back to the command queue260.

Once the data has been stored in the buffer 225 by the storagecontroller 230, the data may be transferred out of the buffer 225 andsent to the host system 205. For example, the memory system controller215 may cause the interface 220 to retrieve the data out of the buffer225 using the data path 250 and transmit the data to the host system205, e.g., according to a protocol (e.g., a UFS protocol or an eMMCprotocol). For example, the interface 220 may process the command fromthe command queue 260 and may indicate to the memory system controller215, e.g., via the bus 235, that the data transmission to the hostsystem 205 has been completed.

The memory system controller 215 may execute received commands accordingto an order (e.g., a first-in, first-out order, according to the orderof the command queue 260). For each command, the memory systemcontroller 215 may cause data corresponding to the command to be movedinto and out of the buffer 225, as discussed above. As the data is movedinto and stored within the buffer 225, the command may remain in thebuffer queue 265. A command may be removed from the buffer queue 265,e.g., by the memory system controller 215, if the processing of thecommand has been completed (e.g., if data corresponding to the accesscommand has been transferred out of the buffer 225). If a command isremoved from the buffer queue 265, the address previously storing thedata associated with that command may be available to store dataassociated with a new command.

The memory system controller 215 may additionally be configured foroperations associated with the one or more memory devices 240. Forexample, the memory system controller 215 may execute or manageoperations such as wear-leveling operations, garbage collectionoperations, error control operations such as error-detecting operationsor error-correcting operations, encryption operations, cachingoperations, media management operations, background refresh, healthmonitoring, and address translations between logical addresses (e.g.,LBAs) associated with commands from the host system 205 and physicaladdresses (e.g., physical block addresses) associated with memory cellswithin the memory devices 240. That is, the host system 205 may issuecommands indicating one or more LBAs and the memory system controller215 may identify one or more physical block addresses indicated by theLBAs. In some cases, one or more contiguous LBAs may correspond tononcontiguous physical block addresses. In some cases, the storagecontroller 230 may be configured to perform one or more of the aboveoperations in conjunction with or instead of the memory systemcontroller 215. In some cases, the memory system controller 215 mayperform the functions of the storage controller 230 and the storagecontroller 230 may be omitted.

As described with reference to FIG. 1 , a memory device 240 may includea cache 285 to improve performance of the memory device 240. The cache285 may include blocks that may be configured to operate in one or moremodes. As described herein, a block operating in a first mode may storefewer bits per memory cell than a block operating in a second mode. Forexample, a block operating in the first mode may store data in an SLCand a block operating in the second mode may store data in amultiple-level memory cell (e.g., MLC, TLC, or QLC). In some examples, ablock operating in the first mode may store data in an MLC and a blockoperating in the second mode may store data in a TLC or QLC.Additionally or alternatively, a block operating in the first mode maystore data in a TLC and a block operating in the second mode may storedata in a QLC.

In some cases, a memory device 240 (e.g., a NAND memory device 240) thatincludes a large quantity of blocks that operate in the second mode mayperform slower operations than a memory device 240 that includes fewerblocks that operate in the second mode. Accordingly, the memory device240 may use a cache 285 including blocks operating in the first mode tohandle relatively low latency procedures. For example, the cache 285 maystore frequently-read data or recently-read data to support relativelylow latency read operations. Additionally or alternatively, the memorysystem 210 may initially write data to the cache 285 to supportrelatively low latency write operations before moving the data from thecache 285 to other memory cells (e.g., higher capacity memory cells ofthe memory device 240, such as TLCs). Different quantities of bits permemory cell may support different endurances and, correspondingly,different quantities of P/E cycles. In one example, an SLC block maysupport 100,000 P/E cycles, an MLC block may support 30,000 P/E cycles,a TLC block may support 8,000 P/E cycles, and a QLC block may support2,000 P/E cycles over the lifetime of each respective block. As such,blocks that operate according to the first mode (e.g., blocks that storefewer bits per memory cell) may support a higher TBW than other blocks.

To improve performance and endurance, some memory devices 240 may employthe cache 285 including blocks that are configured to statically operatein the first mode, such as the static SLC blocks 275. The static SLCblocks 275 may operate according to the first mode for a lifetime of theblocks and may support more endurance and reliability than other blocksin the memory device 240. Although the cache 285 including the staticSLC blocks 275 may store less data than another cache that includesother blocks, the cache 285 may last longer and may support more datacycling (e.g., more write operations and more TBW) than another cache.In some examples, however, the reduced data storage associated with thecache 285 may reduce a capacity of the memory device 240. For example,each static SLC block 275 within the cache 285 may store relatively lessinformation than other blocks of the memory device 240 and may beremoved from an overprovisioning pool for the memory device 240 (e.g., apool of free blocks). Accordingly, the cache 285 may reduceoverprovisioning, increase a write amplification factor, and degradeperformance (e.g., dirty performance) of the memory device 240.

To support a balance between endurance of the memory device 240 andsufficient overprovisioning for the memory device 240, at least aportion of the cache 285 may include dynamic blocks 280. Each dynamicblock 280 may be programmed according to the first mode or the secondmode for each P/E cycle performed on the respective block. In somecases, a P/E cycle that is performed according to the second mode maydecrease an endurance of the dynamic block 280 relatively more than aP/E cycle performed according to the first mode. For example, if data iswritten to a dynamic block 280 in the second mode one or more times, atotal quantity of PIE cycles (e.g., a TBW) supported by the dynamicblock 280 may be reduced to be less than a total quantity of P/E cyclessupported by a block that operates in the first mode (e.g., an SLCblock). Some systems may handle such a dynamic block 280 (e.g.,switching between storing data in SLCs and multiple-level cells) as ifthe block supports a same total quantity of P/E cycles as a blockstatically storing data in the multiple-level cells. However, such asystem may fail to effectively account for the endurance gains providedby the dynamic block 280 periodically or aperiodically storing data inthe SLCs. The degradation of endurance due to P/E cycles in the secondmode may be a product of wear leveling or other procedures performed tocombat the storage of data in the second mode (e.g., the second mode maywear on a block more than the first mode).

As described herein, a memory system controller 215 may calculate aratio of cycles in the first mode to cycles in the second mode that maybe supported by each dynamic block 280 (e.g., a single cycle in thesecond mode may wear the block by an amount that corresponds to thecalculated ratio as compared to a single cycle in the first mode). Thememory system controller 215 may utilize the calculated ratio and aprocess (e.g., an algorithm) to configure the cache 285 to include asubset of the dynamic blocks 280 and to determine whether to programeach dynamic block 280 in the first mode or the second mode as the cache285 is in use, which may provide for a target quantity of P/E cycles tobe performed on each dynamic block 280 while a target endurance of eachdynamic block 280 is maintained. A process for efficiently configuringand dynamically allocating blocks in a cache 285 is described herein andin further detail with reference to FIG. 4 .

The memory system controller 215 may configure the cache 285 with one ormore static SLC blocks 275, dynamic blocks 280, other blocks, or anycombination thereof to achieve a balance between performance, endurance,and capacity for the memory device 240. The memory system controller 215may identify a quantity of blocks that support the second mode (e.g.,blocks that include multiple-level cells) may be allocated within thememory device 240 to achieve a target capacity for the memory device 240(e.g., a threshold capacity to maintain sufficient overprovisioning andstorage capacity). The memory system controller 215 may allocateremaining blocks to the cache 285 to improve performance of the memorydevice 240. The memory system controller 215 may configure a target TBWfor the cache 285 (e.g., a target quantity of data that the cache 285may support) in accordance with a target capacity and endurance for thememory device 240. In some examples, the cache 285 may be allocated witha first quantity of static SLC blocks 275 and a second quantity ofdynamic blocks 280 to support the target TBW for the cache 285.

The memory system controller 215 may configure a target ratio of cyclesperformed in the first mode to cycles performed in the second mode foreach dynamic block 280 in the cache 285. The target ratio, which may bereferred to as a target cycling ratio, may correspond to a respectivefirst target count for P/E cycles in the first mode and a respectivesecond target count for P/E cycles in the second mode. The targetcycling ratio may be calculated for each dynamic block 280 in the cache285 to achieve a balance between endurance and performance of the cache285 (e.g., the target TBW) and capacity targets for the memory device240. For example, each dynamic block 280 may be configured to operate inthe first mode for a first percentage of cycles and in the second modefor a second percentage of cycles, where the first and secondpercentages may be calculated such that the dynamic block 280 maysupport a target TBW (e.g., a target endurance for the cache 285, thememory device 240, or both). In some cases, the memory system controller215 may configure a target ratio for each block of the cache 285, wherethe static SLC blocks 275 are allocated zero cycle counts for the secondmode. In some examples, the cache 285, the target TBW for the cache 285,the target cycling ratios, or any combination thereof may be configured(e.g., pre-configured) during design of the memory device 240.

In some examples, the configured parameters for the cache 285 may bedetermined by the memory system controller 215 or some other componentor controller in accordance with a characterization operation (e.g., aNAND characterization operation), a process (e.g., an algorithm), orboth. The parameters may be calculated and determined to meet the targetTBW for the memory device 240 while reducing an allocation of the staticSLC blocks 275 (e.g., minimizing the allocation of the static SLC blocks275) within the cache 285 (e.g., to obtain zero, or close to zero,static SLC blocks 275 within the cache 285).

Although endurance and performance of the cache 285 may be improved byconfiguring the target TBW and target cycling ratios at design time(e.g., based on or in response to an estimated level of usage for a hostsystem 205), some host systems 205 may write more data to the memorydevice 240 than other host systems, which may affect the configuredparameters. For example, a first host system 205 may frequently writedata to a memory device 240, store a relatively large quantity of dataon the memory device 240, or both. A second host system 205 may writedata to the memory device 240 less frequently than the first host system205, store less data on the memory device 240 than the first host system205, or both. The TBW to the memory device 240 by the first host system205 (e.g., an actual TBW) may be higher than the target TBW for aspecific time period or at a reference time (e.g., after a month ofusage), and the target cycling counts for the cache 285 may not supportthe relatively high level of usage by the first host system 205 (e.g.,the dynamic blocks 280 may operate in the second mode significantly moreoften than the first mode). Additionally or alternatively, the TBW tothe memory device 240 by the second host system 205 may be less than thetarget TBW for the specific time period or at the reference time.Differences between the actual TBW and the target TBW may result in lessendurance, or less capacity, or both, than if the target cycling countsare dynamically determined based on or in response to a level of usageof the memory device 240.

As described herein, the memory system controller 215 may dynamicallyswitch modes for one or more of the dynamic blocks 280, adjust theconfigured target cycling ratio for one or more of the dynamic blocks280, or both according to a level of usage of the memory device 240(e.g., during product runtime). The memory system controller 215 maytrack a first quantity of PIE cycles performed on each dynamic block 280in the cache 285 in the first mode and a second quantity of PIE cyclesperformed on each dynamic block 280 in the second mode. The memorysystem controller 215 may additionally or alternatively track a TBW tothe cache 285. In some examples, the TBW may correspond to a totalquantity of P/E cycles performed on the blocks in the cache 285.Additional aspects directed to components for tracking data associatedwith cache usage may be further described herein, including withreference to FIG. 3 .

The memory system controller 215 may determine whether to program eachdynamic block 280 in the cache 285 in the first mode or the second modebased on or in response to the target cycling ratio for the block. Insome examples, the memory system controller 215 may monitor the targetcycling ratio for the P/E cycles for each dynamic block 280 to determinewhether to switch modes for the respective dynamic block 280.Additionally or alternatively, the memory system controller 215 maymonitor for one or more triggers to switch a dynamic block 280 from thefirst mode to the second mode or from the second mode to the first mode.The one or more triggers may include a capacity of the memory device 240satisfying a threshold capacity, the capacity of the memory device 240failing to satisfy the threshold capacity, a write command for thememory device 240, an erase command for the memory device 240, or anycombination thereof.

In one example, if the capacity of the memory device 240 to store datafalls below the threshold capacity for the memory device 240, the memorydevice 240 or the memory system controller 215 may trigger one or moredynamic blocks 280 in the cache 285 to switch from the first mode to thesecond mode (e.g., to increase the capacity of the memory device 240 tosatisfy the threshold capacity). If the capacity of the memory device240 to store data exceeds the threshold capacity, the memory device 240or the memory system controller 215 may trigger one or more dynamicblocks 280 in the cache 285 to switch from the second mode to the firstmode (e.g., to increase performance while still satisfying the thresholdcapacity). Additionally or alternatively, each write or erase commandreceived for the memory device 240 may trigger the memory systemcontroller 215 to select one or more dynamic blocks 280 to switch modes.For example, if a command indicates to write data to the memory device240, the memory system controller 215 may select one or more dynamicblocks 280 to switch from the first mode to the second mode. If acommand indicates to erase data from the memory device 240, the memorysystem controller 215 may select one or more dynamic blocks 280 toswitch from the second mode to the first mode.

The memory system controller 215 may select the one or more dynamicblocks 280 to switch from the first mode to the second mode or from thesecond mode to the first mode in accordance with the tracked cyclingratio and the target cycling ratio for the one or more dynamic blocks280. The memory system controller 215 may identify a first set of one ormore dynamic blocks 280 that are behind on the cycling ratio. Forexample, a ratio of cycles performed in the first mode to cyclesperformed in the second mode may be less than a target ratio for eachblock in the first set of dynamic blocks 280. The memory systemcontroller 215 may identify a second set of one or more dynamic blocks280 that are ahead on the cycling ratio. For example, a ratio of cyclesperformed in the first mode to cycles performed in the second mode maybe greater than a target ratio for each block in the second set ofdynamic blocks 280. If the memory system controller 215 identifies atrigger to switch dynamic blocks 280 from the second mode to the firstmode, the memory system controller 215 may select one or more dynamicblocks 280 from the first set to program in the first mode. If thememory system controller 215 identifies a trigger to switch dynamicblocks 280 from the first mode to the second mode, the memory systemcontroller 215 may select one or more dynamic blocks 280 from the secondset to program in the second mode. Such a selection procedure may allowthe dynamic blocks 280 to trend towards the target cycling ratio,support more efficient usage of the dynamic blocks 280.

In some examples, the memory system controller 215 may periodically (oraperiodically) determine whether to adjust the target cycling ratios forthe dynamic blocks 280 based on or in response to a TBW to the cache 285(e.g., an actual TBW to the cache 285 by a host system 205). The TBW tothe cache 285 may correspond to data written to the cells operating inthe first mode (e.g., the static SLC blocks 275 and dynamic blocks 280operating as SLC blocks), which may support the relatively low latencyoperations of the cache 285. If the actual TBW to the cache 285 isgreater than the target TBW for the cache 285, the memory systemcontroller 215 may increase a target ratio of cycles performed in thefirst mode to cycles performed in the second mode for one or more of thedynamic blocks 280. The memory system controller 215 may thereby programrelatively more dynamic blocks 280 in the first mode in the cache 285 tohandle the increased wear by the host system 205, which may provide fora longer life of the cache 285 while supporting the relatively heavyworkload (e.g., as compared to if the cycling targets were notadjusted). If the actual TBW to the cache 285 is less than the targetTBW for the cache 285, the memory system controller 215 may decrease atarget ratio of cycles performed in the first mode to cycles performedin the second mode for one or more of the dynamic blocks 280. The memorysystem controller 215 may thereby program relatively more dynamic blocks280 in the second mode in the cache 285 to account for the cache 285experiencing a relatively lower workload than expected (e.g., a lowerworkload than accounted for by the target TBW for the cache 285). Theincreased quantity of dynamic blocks 280 operating in the second modemay support increased total capacity for the memory device 240 andincreased overprovisioning and improved performance of the memory device240 for operations such as wear leveling, garbage collection, and thelike (e.g., dirty performance), while still satisfying the actualworkload of the cache 285. By adjusting one or more of the cyclingtargets based on or in response to the actual TBW for the cache 285, thememory system controller 215 may improve an allocation of blocks in thecache 285 to balance endurance, performance, and capacity for the memorydevice 240 in accordance with a level of usage of the cache 285, thememory device 240, or both.

Additionally or alternatively, the memory system controller 215 maydetermine whether to adjust the target cycling ratios for the dynamicblocks 280 in accordance with a wear leveling status of the dynamicblocks 280. Wear leveling may be tracked, for example, according to aquantity of erases performed on each dynamic block 280. In someexamples, an adjusted wear leveling status may be calculated by applyinga ratio between erases performed in the first mode to erases performedin the second mode to account for the increased wear on a dynamic block280 operating in the second mode. Accordingly, a wear leveling processfor one or more of the dynamic blocks 280 may indicate, to the memorysystem controller 215, that a quantity of erases for the one or moreblocks is exceeding or falling below a threshold quantity, where thequantity may be calculated to account for erases performed in the firstmode and the second mode. The memory system controller 215 may therebyadjust target cycling ratios for the one or more dynamic blocks 280 inaccordance with the indicated wear leveling status.

A memory device 240 as described herein may be configured with a cache285, a target TBW for the cache 285, and target ratios of cyclesperformed in the first mode and cycles performed in the second mode foreach dynamic block 280 within the cache 285 (e.g., at design time). Amemory system controller 215 may monitor a level of usage of the cache285, the memory device 240, or both (e.g., at runtime) to dynamicallyadjust the allocation of the dynamic blocks 280, the target cyclingratios for the dynamic blocks 280, or both to improve performance andoverprovisioning of the memory device 240.

FIG. 3 illustrates an example of a memory system 300 that supports cacheblock budgeting techniques in accordance with examples as disclosedherein. In some examples, the memory system 300 may implement aspects ofthe systems 100 and 200. For example, the memory system 300 may includea memory system controller 315 and a memory device 340, which may beexamples of or include aspects of a memory system controller 215 and amemory device 240 as described with reference to FIGS. 1 and 2 .

Although the various components of the memory system 300 are shown asseparate for illustrative clarity, the components of the memory system300 may be combined in any combination or additional components may beadded. Further, the components may be located differently than shown(e.g., the components may be included in the memory system controller315, or may be included in a storage controller, or may be included inthe memory device 340, among other examples). In some examples, theoperations described as being performed by one component mayadditionally or alternatively be performed by different components. Insome examples, one or more parameters described as being stored in orconfigured by one component may additionally or alternatively be storedin or configured by different components (e.g., a parameter may bestored within a component of the memory system controller 315, withinthe cache 355, within a hard drive of the memory system 300, orelsewhere in the memory system 300).

The memory system 300 may include the memory system controller 315, thememory device 340, and a connection 305 for communicating commandsbetween the memory system controller 315 and the memory device 340. Thememory system controller 315, or various components thereof, may beconfigured to support cache block budgeting techniques for the cache 355in the memory device 340. For example, the memory system controller 315may include a P/E cycle count component 320, a P/E cycle targetcomponent 325, a periodicity component 330, a TBW component 335, a logiccomponent 345, or any combination thereof. Each of these components maycommunicate, directly or indirectly, with one another via one or morebuses 310. The memory device 340 may include a cache 355, which may bean example of the cache 285 as described with reference to FIG. 2 . Thecache 355 may include a first subset of blocks configured to staticallyoperate according to a first mode (e.g., using SLC blocks), a secondsubset of blocks (e.g., the dynamic blocks 350) configured todynamically switch between operating in the first mode and a second mode(e.g., using multiple-level memory cell blocks), one or more subsets ofother blocks, or any combination thereof. The memory system 300 maysupport the first mode, the second mode, one or more other programmingmodes for the dynamic blocks 350 in the cache 355, or a combinationthereof.

As described herein, including with reference to FIG. 2 , the memorysystem controller 315 may configure the memory device 340 with the cache355, a target TBW for the cache 355, a target ratio of cycles performedin the first mode to cycles performed in the second mode for eachdynamic block 350 in the cache 355, or any combination thereof. Thetarget ratio may, in some examples, correspond to a first target cyclecount for the first mode and a second target cycle count for the secondmode for each dynamic block 350. The P/E cycle target component 325 mayconfigure and store the target cycling ratio and target cycle counts fora dynamic block 350 (e.g., with an association to a specific dynamicblock 350, such as a dynamic block identifier). In some cases, each ofthe dynamic blocks 350 may be initially configured with a same targetcycling ratio. The target TBW for the memory device 340 may beconfigured and stored by the TBW component 335. The TBW component 335may additionally or alternatively configure a target capacity and atarget TBW for the memory device 340 (e.g., based on or in response toan estimated level of usage for a host system). The memory systemcontroller 315 may indicate the configuration for the cache 355including the configured parameters to the memory device 340 via theconnection 305 (e.g., command signaling sent using the connection 305).In some examples, the memory device 340 may be configured (e.g.,pre-configured) with the cache 355 and corresponding parameters.

As the memory device 340 is accessed by a host system (e.g., during aproduct runtime), the P/E cycle count component 320 may track a ratio ofcycles performed in the first mode to cycles performed in the secondmode for each dynamic block 350 in the cache 355. The memory systemcontroller 315 (e.g., using the P/E cycle count component 320) may storethe ratio of cycles performed for each dynamic block 350 and update thestored ratio throughout the lifetime of the memory device 340.Additionally or alternatively, during runtime, the TBW component 335 maytrack a TBW to the cache 355. The memory system controller 315 (e.g.,using the TBW component 335) may store the TBW to the cache 355 (e.g.,an actual TBW) and the target TBW configured for the cache 355. In someexamples, the TBW component 335 may determine the TBW to the cache 355based on or in response to a quantity of cycles performed for eachdynamic block 350, which may be tracked by the P/E cycle count component320.

The periodicity component 330 may determine a periodicity or otherschedule (e.g., an aperiodic schedule) for monitoring and in someexamples updating target cycling ratios for the dynamic blocks 350 inthe cache 355. The periodicity may be determined based on or in responseto an estimated level of usage by the host system. If the periodicity isrelatively short, the memory system controller 315 may account forirregular data (e.g., data that may not accurately represent the hostsystem's typical usage). As such, the periodicity component 330 mayselect a periodicity that provides sufficient time for obtainingaccurate host system data usage (e.g., the periodicity may be days,weeks, months, or some other duration).

The one or more triggers for switching the dynamic blocks 350 from thefirst mode to the second mode or from the second mode to the first mode,as described with reference to FIG. 2 , may be identified by the logiccomponent 345. For example, the logic component may identify if a writecommand is received for the memory device 340, if an erase command isreceived for the memory device 340, whether a capacity of the memorydevice 340 is above or below a threshold capacity, whether a capacity ofthe cache 355 is above or below a threshold capacity, or any combinationthereof.

The logic component 345 may select one or more of the dynamic blocks 350to switch from the first mode to the second mode or from the second modeto the first mode in response to identifying one or more of the triggersand in accordance with the cycle counts for the one or more dynamicblocks 350, as described with reference to FIG. 2 . The logic component345 may receive signaling indicating a first cycle count in the firstmode and a second cycle count in the second mode (e.g., current cyclecounts) for each dynamic block 350 from the P/E cycle count component320. The logic component 345 may receive signaling indicating a targetcycle ratio for each dynamic block 350 from the P/E cycle targetcomponent 325. The logic component 345 may compare the first and secondcycle counts within the periodicity interval with the target cyclingratio to identify a first set of dynamic blocks 350 that are associatedwith a lesser ratio of cycles in the first mode to cycles in the secondmode than the target cycling ratio and a second set of dynamic blocks350 that are associated with a greater ratio of cycles in the first modeto cycles in the second mode than the target cycling ratio.

If the logic component 345 determines relatively more dynamic blocks 350may be programmed in the first mode (e.g., in response to identifying atrigger), the logic component 345 may select one or more dynamic blocks350 from the first set. If the logic component 345 determines relativelymore dynamic blocks 350 may be programmed in the second mode (e.g., inresponse to identifying a trigger), the logic component 345 may selectone or more dynamic blocks 350 from the second set. The logic component345 may send an indication of the selected blocks and the respectivemode for programming the selected blocks to the memory device 340 overthe connection 305.

The logic component 345 may adjust the cycling targets for one or moreof the dynamic blocks 350 according to a level of usage of the memorydevice 340 and the cache 355, as described with reference to FIG. 2 .The logic component 345 may compare a current TBW to the cache 355 withan adjusted target TBW (e.g., a second threshold TBW) for the cache 355at one or more intervals in accordance with the periodicity indicated bythe periodicity component 330. The logic component 345 may receivesignaling indicating the current TBW and the second threshold TBW forthe cache 355 from the TBW component 335. In some examples, the TBWcomponent 335 may calculate the second threshold TBW based on or inresponse to the target TBW (e.g., a first threshold TBW) for the cache355 and the periodicity. In one example, if a lifetime of the cache 355is three years and the periodicity is six months, the second thresholdTBW for a first interval (e.g., the first six months of using the cache355) may be one sixth of the target TBW for the cache 355.

If the TBW to the cache 355 during the periodicity interval is less thanthe second threshold TBW for the cache 355, the logic component 345 mayindicate a decreased first target count for the first mode and anincreased second target count for the second mode for the one or moredynamic blocks 350 to the P/E cycle target component 325. If the TBW tothe cache 355 during the periodicity interval is greater than the secondthreshold TBW for the cache 355, the logic component 345 may indicate anincreased first target count for the first mode and a decreased secondtarget count for the second mode for the one or more dynamic blocks 350to the P/E cycle target component 325. The P/E cycle target component325 may store the updated target cycling counts accordingly.Alternatively, the logic component 345 may determine not to update thetarget cycling counts based on or in response to the TBW to the cache355 during the periodicity interval being relatively close to the secondthreshold TBW for the cache 355 (e.g., within an error threshold).

Additionally or alternatively, the logic component 345 may determine(e.g., track) a wear leveling status for the dynamic blocks 350 based onor in response to a quantity of erases performed on the dynamic blocks350 within each periodicity interval, as described with reference toFIG. 2 . The logic component 345 may select one or more dynamic blocks350 to program according to the first mode or the second mode inresponse to determining the wear leveling status.

A memory system controller 315 may thereby include one or morecomponents for configuring a memory device 340 with a cache 355, atarget TBW for the cache 355, and target cycling ratios for each dynamicblock 350 within the cache 355. The memory system controller 315 mayinclude one or more components for dynamically switching modes forprogramming the dynamic blocks 350, adjusting the target cycling ratiosfor the dynamic blocks 350, or both, to improve performance andoverprovisioning.

FIG. 4 illustrates an example of a flow diagram 400 that supports cacheblock budgeting techniques in accordance with examples as disclosedherein. The flow diagram 400 may illustrate a process that may beimplemented by a system 100 (or one or more components thereof), asystem 200 (or one or more components thereof), or a memory system 300(or one or more components thereof) as described with reference to FIGS.1-3 . The flow diagram 400 may illustrate a process for managing blockswithin a cache to improve performance, endurance, and capacity of thecache and a corresponding memory device, as described with reference toFIGS. 1-3 .

Aspects of the flow diagram 400 may be implemented by a controller(e.g., a memory system controller), among other components. Additionallyor alternatively, aspects of the flow diagram 400 may be implemented asinstructions stored in memory (e.g., firmware stored in a memory coupledwith a memory device, the memory system controller, or both). Forexample, the instructions, if executed by a controller (e.g., the memorysystem controller or a storage controller), may cause the controller toperform the operations of the flow diagram 400. Alternative examples ofthe flow diagram 400 may be implemented in which some operations areperformed in a different order than described or are not performed atall. In some cases, operations may include features not mentioned below,or additional operations may be added.

At 405, a memory device is configured with a cache. For example, thememory device may receive a configuration for a cache from a memorysystem controller. The configuration may be received at a controller orother component of the memory device. The configuration may indicate afirst subset of blocks in the cache configured to statically operate ina first mode and a second subset of blocks in the cache configured todynamically switch between operating in the first mode and a secondmode. As described with reference to FIGS. 1-3 , a block operating inthe first mode may be configured to store a first quantity of bits permemory cell and a block operating in the second mode may be configuredto store a second quantity of bits per memory cell that is greater thanthe first quantity of bits per memory cell.

At 410, each block of the second subset of blocks (e.g., the dynamicblocks) in the cache may be assigned with a target ratio of cyclesperformed in the first mode to cycles performed in the second modeaccording to a respective first target count for the first mode and arespective second target count for the second mode. The target ratio ofcycles for each block may be configured based on or in response to athreshold TBW for the cache.

At 415, a respective ratio of cycles performed in the first mode tocycles performed in the second mode for each block of the second subsetof blocks in the cache may be tracked, stored, or both. In someexamples, the memory system controller may track and store therespective ratio as the memory device is used by a host system.

At 420, it may be determined whether a first trigger to switch a blockof the second subset of blocks from the first mode to the second mode isset. The first trigger may be a capacity of the memory device failing tosatisfy a threshold capacity, a command indicating to write data to thememory device, or both. At 425, if the first trigger is set (e.g., atrigger bit is set to a value indicating that the memory system detectedthe first trigger), it may be determined whether a ratio for a block(e.g., as tracked at 415) is greater than a respective target ratio forthe block. For example, it may be determined whether a quantity of P/Ecycles performed in the first mode is greater than a target quantity ofP/E cycles in the first mode for the block.

At 430, if the respective ratio is greater than the target ratio for theblock (e.g., the ratio of PIE cycles performed in the first mode to P/Ecycles performed in the second mode is greater than the target ratio),the block may be selected. For example, the block may be selected fromthe second subset of blocks to switch from the first mode to the secondmode responsive to identifying the first trigger. In some examples, thememory system controller may select the block and program the block inthe second mode for a subsequent P/E cycle. At 435, if the respectiveratio is less than the target ratio for the block (e.g., the ratio ofP/E cycles performed in the first mode to P/E cycles performed in thesecond mode is less than the target ratio), another block may beselected and the block may remain in the first mode for one or moresubsequent cycles.

At 440, if the first trigger is not set (e.g., if the first trigger isnot identified), it may be determined whether a second trigger to switcha block of the second subset of blocks from the second mode to the firstmode is set. The second trigger may be a capacity of the memory devicesatisfying a threshold capacity, a command indicating to delete datafrom the memory device, or both.

At 445, if the second trigger is set (e.g., if the second trigger isidentified), it may be determined whether a ratio for the block (e.g.,as tracked at 415) is less than a respective target ratio for the block.For example, it may be determined whether a ratio of P/E cyclesperformed in the first mode to P/E cycles performed in the second modeis less than the target ratio.

At 450, if the respective ratio is less than the target ratio for theblock, the block may be selected. For example, the block may be selectedfrom the second subset of blocks to switch from the second mode to thefirst mode responsive to identifying the first trigger. In someexamples, the memory system controller may select the block and programthe block in the first mode for a subsequent P/E cycle. At 455, if therespective ratio is greater than the target ratio for the block, anotherblock may be selected and the block may remain in the second mode forone or more subsequent cycles.

At 460, it may be determined whether a periodicity has expired. In someexamples, the periodicity may be a configured periodicity. Theperiodicity may be configured, stored, or both, by a periodicitycomponent of the memory system controller, as described with referenceto FIG. 3 . If the periodicity has not expired, the process may repeat.For example, the memory system controller may continue to trackrespective ratios of cycles for the dynamic blocks at 415.

At 465, if the periodicity has expired, it may be determined whether acurrent TBW for the cache is less than a second threshold TBW for thecache. The second threshold TBW may be calculated in accordance with thethreshold TBW configured for the cache and a timing associated with theperiodicity. For example, if the periodicity expires six timesthroughout a life of the memory system, the second threshold TBW at afirst time the periodicity expires may be one sixth of the threshold TBWfor the cache. The second threshold TBW at a second time the periodicityexpires may be two sixths of the threshold TBW for the cache. In someexamples, the TBW for the cache, the threshold TBW for the cache, thesecond threshold TBW for the cache, or any combination thereof, may beconfigured, tracked, or stored by the memory system controller, asdescribed with reference to FIG. 3 .

At 470, if the TBW for the cache is less than the second threshold TBWfor the cache, a first target count for the first mode for at least oneblock of the second subset of blocks may be decreased and a secondtarget count for the second mode for the at least one block of thesecond subset of blocks may be increased. Accordingly, a target ratio ofcycles performed in the first mode to cycles performed in the secondmode for at least one dynamic block may decrease. In some examples, aP/E cycle target component of the memory system controller may adjustthe target ratio for the at least one block and may store the adjustedratio, as described with reference to FIG. 3 .

At 475, if the TBW for the cache is greater than or equal to the secondthreshold TBW for the cache, it may be determined whether the currentTBW for the cache is greater than a third threshold TBW for the cache.In some examples, the third threshold TBW may be the same as the secondthreshold TBW. Additionally or alternatively, the third TBW may bedifferent than (e.g., greater than) the second threshold TBW, such thatthe targets may not be adjusted if the actual TBW for the cache fallswithin the range between the second threshold TBW and the thirdthreshold TBW for the cache. The third threshold TBW may be calculatedin accordance with the threshold TBW for the cache and the periodicity.

At 480, if the TBW for the cache is greater than the third threshold TBWfor the cache, a first target count for the first mode for at least oneblock of the second subset of blocks may be increased and a secondtarget count for the second mode for the at least one block of thesecond subset of blocks may be decreased. Accordingly, a target ratio ofcycles performed in the first mode to cycles performed in the secondmode for at least one dynamic block may increase.

If the actual TBW for the cache is less than or equal to the thirdthreshold TBW for the cache, the target ratio of cycles may bemaintained. For example, the memory system controller may refrain fromadjusting one or more target ratios based on or in response to theactual TBW for the cache being within a threshold range of the targetTBW for the cache. Upon either adjusting or determining not to adjustthe target ratios, the memory system controller may continue to trackrespective ratios of cycles for the dynamic blocks at 415.

FIG. 5 shows a block diagram 500 of a memory system 520 that supportscache block budgeting techniques in accordance with examples asdisclosed herein. The memory system 520 may be an example of aspects ofa memory system 110, 210, or 300, as described with reference to FIGS.1-3 . The memory system 520, or various components thereof, may be anexample of means for performing various aspects of cache block budgetingtechniques as described herein. For example, the memory system 520 mayinclude a cache configuration component 525, a cycling ratio component530, a block selection component 535, a target cycling ratio component540, a trigger component 545, a TBW component 550, or any combinationthereof. Each of these components may communicate, directly orindirectly, with one another (e.g., via one or more buses).

The cache configuration component 525 may be configured as or otherwisesupport a means for configuring a memory device with a cache including afirst subset of blocks configured to statically operate in a first modeand a second subset of blocks configured to dynamically switch betweenoperating in the first mode and a second mode, where a first blockoperating in the first mode is configured to store a first quantity ofbits per memory cell and a second block operating in the second mode isconfigured to store a second quantity of bits greater than the firstquantity of bits per memory cell. The cycling ratio component 530 may beconfigured as or otherwise support a means for storing, for each blockof the second subset of blocks, a respective ratio of cycles performedin the first mode to cycles performed in the second mode. The blockselection component 535 may be configured as or otherwise support ameans for selecting a block from the second subset of blocks to switchfrom the first mode to the second mode or from the second mode to thefirst mode responsive to a trigger and based on (e.g., using) therespective ratio for the block.

In some examples, the target cycling ratio component 540 may beconfigured as or otherwise support a means for assigning, based on(e.g., in response to) a threshold TBW for the cache, each block of thesecond subset of blocks a respective target ratio of cycles performed inthe first mode to cycles performed in the second mode according to arespective first target count for the first mode and a respective secondtarget count for the second mode.

In some examples, the trigger component 545 may be configured as orotherwise support a means for identifying the trigger to switch theblock from the first mode to the second mode. In some examples, thecycling ratio component 530 may be configured as or otherwise support ameans for determining the respective ratio for the block is greater thanthe respective target ratio for the block based on (e.g., in responseto) identifying the trigger, where the block is selected based on (e.g.,in response to) the determining. In some examples, the trigger includesa current capacity of the memory device failing to satisfy a thresholdcapacity, a command indicating to write data to the memory device, orboth.

In some examples, the trigger component 545 may be configured as orotherwise support a means for identifying the trigger to switch theblock from the second mode to the first mode. In some examples, thecycling ratio component 530 may be configured as or otherwise support ameans for determining the respective ratio for the block is less thanthe respective target ratio for the block based on (e.g., in responseto) identifying the trigger, where the block is selected based on (e.g.,in response to) the determining. In some examples, the trigger includesa current capacity of the memory device satisfying a threshold capacity,a command indicating to delete data from the memory device, or both.

In some examples, the TBW component 550 may be configured as orotherwise support a means for comparing a current TBW for the cache at afirst time to a second threshold TBW for the cache at the first time,the second threshold TBW being based on (e.g., calculated using) thethreshold TBW for the cache and the first time. In some examples, thetarget cycling ratio component 540 may be configured as or otherwisesupport a means for modifying a target ratio for at least one block ofthe second subset of blocks based on (e.g., in response to) thecomparing.

In some examples, the current TBW for the cache is less than the secondthreshold TBW for the cache at the first time, and the target cyclingratio component 540 may be configured as or otherwise support a meansfor modifying the target cycling ratio by decreasing a first targetcycling count for the first mode for the at least one block of thesecond subset of blocks based on (e.g., in response to) the current TBWbeing less than the second threshold TBW and increasing a second targetcycling count for the second mode for the at least one block of thesecond subset of blocks based on (e.g., in response to) the current TBWbeing less than the second threshold TBW.

In some examples, the current TBW for the cache is greater than thesecond threshold TBW for the cache at the first time, and the targetcycling ratio component 540 may be configured as or otherwise support ameans for modifying the target cycling ratio by increasing a firsttarget count for the first mode for the at least one block of the secondsubset of blocks based on (e.g., in response to) the current TBW beinggreater than the second threshold TBW and decreasing a second targetcount for the second mode for the at least one block of the secondsubset of blocks based on (e.g., in response to) the current TBW beinggreater than the second threshold TBW. In some examples, the comparingis performed according to a configured periodicity.

In some examples, the cache configuration component 525 may beconfigured as or otherwise support a means for assigning the firstsubset of blocks and the second subset of blocks to the cache based on(e.g., in response to) a threshold capacity for the memory device. Insome examples, the cache configuration component 525 may be configuredas or otherwise support a means for assigning blocks to the first subsetof blocks or the second subset of blocks based on (e.g., in response to)a threshold TBW for the cache.

In some examples, the first block operating in the first mode storesfirst data in an SLC and the second block operating in the second modestores second data in an MLC, a TLC, or a QLC. In some examples, thefirst block operating in the first mode stores first data in an MLC andthe second block operating in the second mode stores second data in aTLC or a QLC. In some examples, the first block operating in the firstmode stores first data in a TLC and the second block operating in thesecond mode stores second data in a QLC. In some examples, the memorydevice includes a NAND memory device.

FIG. 6 shows a flowchart illustrating a method 600 that supports cacheblock budgeting techniques in accordance with examples as disclosedherein. The operations of method 600 may be implemented by a memorysystem or its components as described herein. For example, theoperations of method 600 may be performed by a memory system asdescribed with reference to FIGS. 1-5 . In some examples, a memorysystem may execute a set of instructions to control the functionalelements of the device to perform the described functions. Additionallyor alternatively, the memory system may perform aspects of the describedfunctions using special-purpose hardware.

At 605, the method may include configuring a memory device with a cacheincluding a first subset of blocks configured to statically operate in afirst mode and a second subset of blocks configured to dynamicallyswitch between operating in the first mode and a second mode, where afirst block operating in the first mode is configured to store a firstquantity of bits per memory cell and a second block operating in thesecond mode is configured to store a second quantity of bits greaterthan the first quantity of bits per memory cell. The operations of 605may be performed in accordance with examples as disclosed herein. Insome examples, aspects of the operations of 605 may be performed by acache configuration component 525 as described with reference to FIG. 5.

At 610, the method may include storing, for each block of the secondsubset of blocks, a respective ratio of cycles performed in the firstmode to cycles performed in the second mode. The operations of 610 maybe performed in accordance with examples as disclosed herein. In someexamples, aspects of the operations of 610 may be performed by a cyclingratio component 530 as described with reference to FIG. 5 .

At 615, the method may include selecting a block from the second subsetof blocks to switch from the first mode to the second mode or from thesecond mode to the first mode responsive to a trigger and based on therespective ratio for the block. The operations of 615 may be performedin accordance with examples as disclosed herein. In some examples,aspects of the operations of 615 may be performed by a block selectioncomponent 535 as described with reference to FIG. 5 .

In some examples, an apparatus as described herein may perform a methodor methods, such as the method 600. The apparatus may include, features,circuitry, logic, means, or instructions (e.g., a non-transitorycomputer-readable medium storing instructions executable by a processor)for configuring a memory device with a cache including a first subset ofblocks configured to statically operate in a first mode and a secondsubset of blocks configured to dynamically switch between operating inthe first mode and a second mode, where a first block operating in thefirst mode is configured to store a first quantity of bits per memorycell and a second block operating in the second mode is configured tostore a second quantity of bits greater than the first quantity of bitsper memory cell, storing, for each block of the second subset of blocks,a respective ratio of cycles performed in the first mode to cyclesperformed in the second mode, and selecting a block from the secondsubset of blocks to switch from the first mode to the second mode orfrom the second mode to the first mode responsive to a trigger and basedon the respective ratio for the block.

Some examples of the method 600 and the apparatus described herein mayfurther include operations, features, circuitry, logic, means, orinstructions for assigning, based on a threshold TBW for the cache, eachblock of the second subset of blocks a respective target ratio of cyclesperformed in the first mode to cycles performed in the second modeaccording to a respective first target count for the first mode and arespective second target count for the second mode.

Some examples of the method 600 and the apparatus described herein mayfurther include operations, features, circuitry, logic, means, orinstructions for identifying the trigger to switch the block from thefirst mode to the second mode and determining the respective ratio forthe block may be greater than the respective target ratio for the blockbased on identifying the trigger, where the block may be selected basedon the determining. In some examples of the method 600 and the apparatusdescribed herein, the trigger includes a current capacity of the memorydevice failing to satisfy a threshold capacity, a command indicating towrite data to the memory device, or both.

Some examples of the method 600 and the apparatus described herein mayfurther include operations, features, circuitry, logic, means, orinstructions for identifying the trigger to switch the block from thesecond mode to the first mode and determining the respective ratio forthe block may be less than the respective target ratio for the blockbased on identifying the trigger, where the block may be selected basedon the determining. In some examples of the method 600 and the apparatusdescribed herein, the trigger includes a current capacity of the memorydevice satisfying a threshold capacity, a command indicating to deletedata from the memory device, or both.

Some examples of the method 600 and the apparatus described herein mayfurther include operations, features, circuitry, logic, means, orinstructions for comparing a current TBW for the cache at a first timeto a second threshold TBW for the cache at the first time, the secondthreshold TBW being based on the threshold TBW for the cache and thefirst time and modifying a target ratio for at least one block of thesecond subset of blocks based on the comparing.

In some examples of the method 600 and the apparatus described herein,the current TBW for the cache may be less than the second threshold TBWfor the cache at the first time, and the modifying the target cyclingratio may include decreasing a first target cycling count for the firstmode for the at least one block of the second subset of blocks based onthe current TBW being less than the second threshold TBW, and increasinga second target cycling count for the second mode for the at least oneblock of the second subset of blocks based on the current TBW being lessthan the second threshold TBW.

In some examples of the method 600 and the apparatus described herein,the current TBW for the cache may be greater than the second thresholdTBW for the cache at the first time, and the modifying the targetcycling ratio may include increasing a first target count for the firstmode for the at least one block of the second subset of blocks based onthe current TBW being greater than the second threshold TBW, anddecreasing a second target count for the second mode for the at leastone block of the second subset of blocks based on the current TBW beinggreater than the second threshold TBW. In some examples of the method600 and the apparatus described herein, the comparing may be performedaccording to a configured periodicity.

Some examples of the method 600 and the apparatus described herein mayfurther include operations, features, circuitry, logic, means, orinstructions for assigning the first subset of blocks and the secondsubset of blocks to the cache based on a threshold capacity for thememory device. Some examples of the method 600 and the apparatusdescribed herein may further include operations, features, circuitry,logic, means, or instructions for assigning blocks to the first subsetof blocks or the second subset of blocks based on a threshold TBW forthe cache.

In some examples of the method 600 and the apparatus described herein,the first block operating in the first mode stores first data in an SLCand the second block operating in the second mode stores second data inan MLC, a TLC, or a QLC, the first block operating in the first modestores first data in an MLC and the second block operating in the secondmode stores second data in a TLC or a QLC, or the first block operatingin the first mode stores first data in a TLC and the second blockoperating in the second mode stores second data in a QLC.

In some examples of the method 600 and the apparatus described herein,the memory device includes a NAND memory device.

It should be noted that the methods described above describe possibleimplementations, and that the operations and the steps may be rearrangedor otherwise modified and that other implementations are possible.Further, portions from two or more of the methods may be combined.

Information and signals described herein may be represented using any ofa variety of different technologies and techniques. For example, data,instructions, commands, information, signals, bits, symbols, and chipsthat may be referenced throughout the above description may berepresented by voltages, currents, electromagnetic waves, magneticfields or particles, optical fields or particles, or any combinationthereof. Some drawings may illustrate signals as a single signal;however, the signal may represent a bus of signals, where the bus mayhave a variety of bit widths.

The terms “electronic communication,” “conductive contact,” “connected,”and “coupled” may refer to a relationship between components thatsupports the flow of signals between the components. Components areconsidered in electronic communication with (or in conductive contactwith or connected with or coupled with) one another if there is anyconductive path between the components that can, at any time, supportthe flow of signals between the components. At any given time, theconductive path between components that are in electronic communicationwith each other (or in conductive contact with or connected with orcoupled with) may be an open circuit or a closed circuit based on theoperation of the device that includes the connected components. Theconductive path between connected components may be a direct conductivepath between the components or the conductive path between connectedcomponents may be an indirect conductive path that may includeintermediate components, such as switches, transistors, or othercomponents. In some examples, the flow of signals between the connectedcomponents may be interrupted for a time, for example, using one or moreintermediate components such as switches or transistors.

The term “coupling” refers to a condition of moving from an open-circuitrelationship between components in which signals are not presentlycapable of being communicated between the components over a conductivepath to a closed-circuit relationship between components in whichsignals are capable of being communicated between components over theconductive path. If a component, such as a controller, couples othercomponents together, the component initiates a change that allowssignals to flow between the other components over a conductive path thatpreviously did not permit signals to flow.

The term “isolated” refers to a relationship between components in whichsignals are not presently capable of flowing between the components.Components are isolated from each other if there is an open circuitbetween them. For example, two components separated by a switch that ispositioned between the components are isolated from each other if theswitch is open. If a controller isolates two components, the controlleraffects a change that prevents signals from flowing between thecomponents using a conductive path that previously permitted signals toflow.

The terms “if,” “when,” “based on,” or “based at least in part on” maybe used interchangeably. In some examples, if the terms “if,” “when,”“based on,” or “based at least in part on” are used to describe aconditional action, a conditional process, or connection betweenportions of a process, the terms may be interchangeable.

The term “in response to” may refer to one condition or action occurringat least partially, if not fully, as a result of a previous condition oraction. For example, a first condition or action may be performed andsecond condition or action may at least partially occur as a result ofthe previous condition or action occurring (whether directly after orafter one or more other intermediate conditions or actions occurringafter the first condition or action).

Additionally, the terms “directly in response to” or “in direct responseto” may refer to one condition or action occurring as a direct result ofa previous condition or action. In some examples, a first condition oraction may be performed and second condition or action may occurdirectly as a result of the previous condition or action occurringindependent of whether other conditions or actions occur. In someexamples, a first condition or action may be performed and secondcondition or action may occur directly as a result of the previouscondition or action occurring, such that no other intermediateconditions or actions occur between the earlier condition or action andthe second condition or action or a limited quantity of one or moreintermediate steps or actions occur between the earlier condition oraction and the second condition or action. Any condition or actiondescribed herein as being performed “based on,” “based at least in parton,” or “in response to” some other step, action, event, or conditionmay additionally or alternatively (e.g., in an alternative example) beperformed “in direct response to” or “directly in response to” suchother condition or action unless otherwise specified.

The devices discussed herein, including a memory array, may be formed ona semiconductor substrate, such as silicon, germanium, silicon-germaniumalloy, gallium arsenide, gallium nitride, etc. In some examples, thesubstrate is a semiconductor wafer. In some other examples, thesubstrate may be a silicon-on-insulator (SOI) substrate, such assilicon-on-glass (SOG) or silicon-on-sapphire (SOP), or epitaxial layersof semiconductor materials on another substrate. The conductivity of thesubstrate, or sub-regions of the substrate, may be controlled throughdoping using various chemical species including, but not limited to,phosphorous, boron, or arsenic. Doping may be performed during theinitial formation or growth of the substrate, by ion-implantation, or byany other doping means.

A switching component or a transistor discussed herein may represent afield-effect transistor (FET) and comprise a three terminal deviceincluding a source, drain, and gate. The terminals may be connected toother electronic elements through conductive materials, e.g., metals.The source and drain may be conductive and may comprise a heavily-doped,e.g., degenerate, semiconductor region. The source and drain may beseparated by a lightly-doped semiconductor region or channel. If thechannel is n-type (i.e., majority carriers are electrons), then the FETmay be referred to as an n-type FET. If the channel is p-type (i.e.,majority carriers are holes), then the FET may be referred to as ap-type FET. The channel may be capped by an insulating gate oxide. Thechannel conductivity may be controlled by applying a voltage to thegate. For example, applying a positive voltage or negative voltage to ann-type FET or a p-type FET, respectively, may result in the channelbecoming conductive. A transistor may be “on” or “activated” if avoltage greater than or equal to the transistor's threshold voltage isapplied to the transistor gate. The transistor may be “off” or“deactivated” if a voltage less than the transistor's threshold voltageis applied to the transistor gate.

The description set forth herein, in connection with the appendeddrawings, describes example configurations and does not represent allthe examples that may be implemented or that are within the scope of theclaims. The term “exemplary” used herein means “serving as an example,instance, or illustration” and not “preferred” or “advantageous overother examples.” The detailed description includes specific details toproviding an understanding of the described techniques. Thesetechniques, however, may be practiced without these specific details. Insome instances, well-known structures and devices are shown in blockdiagram form to avoid obscuring the concepts of the described examples.

In the appended figures, similar components or features may have thesame reference label. Further, various components of the same type maybe distinguished by following the reference label by a hyphen and asecond label that distinguishes among the similar components. If justthe first reference label is used in the specification, the descriptionis applicable to any one of the similar components having the same firstreference label irrespective of the second reference label.

The functions described herein may be implemented in hardware, softwareexecuted by a processor, firmware, or any combination thereof. Ifimplemented in software executed by a processor, the functions may bestored on or transmitted over, as one or more instructions or code, acomputer-readable medium. Other examples and implementations are withinthe scope of the disclosure and appended claims. For example, due to thenature of software, functions described above can be implemented usingsoftware executed by a processor, hardware, firmware, hardwiring, orcombinations of any of these. Features implementing functions may alsobe physically located at various positions, including being distributedsuch that portions of functions are implemented at different physicallocations.

For example, the various illustrative blocks and components described inconnection with the disclosure herein may be implemented or performedwith a general-purpose processor, a DSP, an ASIC, an FPGA or otherprogrammable logic device, discrete gate or transistor logic, discretehardware components, or any combination thereof designed to perform thefunctions described herein. A general-purpose processor may be amicroprocessor, but in the alternative, the processor may be anyprocessor, controller, microcontroller, or state machine. A processormay be implemented as a combination of computing devices (e.g., acombination of a DSP and a microprocessor, multiple microprocessors, oneor more microprocessors in conjunction with a DSP core, or any othersuch configuration).

As used herein, including in the claims, “or” as used in a list of items(for example, a list of items prefaced by a phrase such as “at least oneof” or “one or more of”) indicates an inclusive list such that, forexample, a list of at least one of A, B, or C means A or B or C or AB orAC or BC or ABC (i.e., A and B and C). Also, as used herein, the phrase“based on” shall not be construed as a reference to a closed set ofconditions. For example, an exemplary step that is described as “basedon condition A” may be based on both a condition A and a condition Bwithout departing from the scope of the present disclosure. In otherwords, as used herein, the phrase “based on” shall be construed in thesame manner as the phrase “based at least in part on.”

Computer-readable media includes both non-transitory computer storagemedia and communication media including any medium that facilitatestransfer of a computer program from one place to another. Anon-transitory storage medium may be any available medium that can beaccessed by a general purpose or special purpose computer. By way ofexample, and not limitation, non-transitory computer-readable media cancomprise RAM, ROM, electrically erasable programmable read-only memory(EEPROM), compact disk (CD) ROM or other optical disk storage, magneticdisk storage or other magnetic storage devices, or any othernon-transitory medium that can be used to carry or store desired programcode means in the form of instructions or data structures and that canbe accessed by a general-purpose or special-purpose computer, or ageneral-purpose or special-purpose processor. Also, any connection isproperly termed a computer-readable medium. For example, if the softwareis transmitted from a website, server, or other remote source using acoaxial cable, fiber optic cable, twisted pair, digital subscriber line(DSL), or technologies such as infrared, radio, and microwave, then thecoaxial cable, fiber optic cable, twisted pair, DSL, or technologiessuch as infrared, radio, and microwave are included in the definition ofmedium. Disk and disc, as used herein, include CD, laser disc, opticaldisc, digital versatile disc (DVD), floppy disk, and Blu-ray disc, wheredisks usually reproduce data magnetically, while discs reproduce dataoptically with lasers. Combinations of the above are also includedwithin the scope of computer-readable media.

The description herein is provided to enable a person skilled in the artto make or use the disclosure. Various modifications to the disclosurewill be apparent to those skilled in the art, and the generic principlesdefined herein may be applied to other variations without departing fromthe scope of the disclosure. Thus, the disclosure is not limited to theexamples and designs described herein but is to be accorded the broadestscope consistent with the principles and novel features disclosedherein.

What is claimed is:
 1. An apparatus, comprising: a memory device; and acontroller coupled with the memory device and configured to cause theapparatus to: configure the memory device with a cache comprising afirst subset of blocks configured to statically operate in a first modeand a second subset of blocks configured to dynamically switch betweenoperating in the first mode and a second mode, wherein a first blockoperating in the first mode is configured to store a first quantity ofbits per memory cell and a second block operating in the second mode isconfigured to store a second quantity of bits greater than the firstquantity of bits per memory cell; store, for each block of the secondsubset of blocks, a respective ratio of cycles performed in the firstmode to cycles performed in the second mode; and select a block from thesecond subset of blocks to switch from the first mode to the second modeor from the second mode to the first mode responsive to a trigger andbased at least in part on the respective ratio for the block.
 2. Theapparatus of claim 1, wherein the controller is further configured tocause the apparatus to: assign, based at least in part on a thresholdtotal bytes written (TBW) for the cache, each block of the second subsetof blocks a respective target ratio of cycles performed in the firstmode to cycles performed in the second mode according to a respectivefirst target count for the first mode and a respective second targetcount for the second mode.
 3. The apparatus of claim 2, wherein thecontroller is further configured to cause the apparatus to: identify thetrigger to switch the block from the first mode to the second mode; anddetermine the respective ratio for the block is greater than therespective target ratio for the block based at least in part onidentifying the trigger, wherein the block is selected based at least inpart on the determining.
 4. The apparatus of claim 3, wherein thetrigger comprises a current capacity of the memory device failing tosatisfy a threshold capacity, a command indicating to write data to thememory device, or both.
 5. The apparatus of claim 2, wherein thecontroller is further configured to cause the apparatus to: identify thetrigger to switch the block from the second mode to the first mode; anddetermine the respective ratio for the block is less than the respectivetarget ratio for the block based at least in part on identifying thetrigger, wherein the block is selected based at least in part on thedetermining.
 6. The apparatus of claim 5, wherein the trigger comprisesa current capacity of the memory device satisfying a threshold capacity,a command indicating to delete data from the memory device, or both. 7.The apparatus of claim 2, wherein the controller is further configuredto cause the apparatus to: compare a current TBW for the cache at afirst time to a second threshold TBW for the cache at the first time,the second threshold TBW being based at least in part on the thresholdTBW for the cache and the first time; and modify a target ratio for atleast one block of the second subset of blocks based at least in part onthe comparing.
 8. The apparatus of claim 7, wherein: the current TBW forthe cache is less than the second threshold TBW for the cache at thefirst time; and the controller configured to cause the apparatus tomodify the target ratio is configured to cause the apparatus to:decrease a first target count for the first mode for the at least oneblock of the second subset of blocks based at least in part on thecurrent TBW being less than the second threshold TBW; and increase asecond target count for the second mode for the at least one block ofthe second subset of blocks based at least in part on the current TBWbeing less than the second threshold TBW.
 9. The apparatus of claim 7,wherein: the current TBW for the cache is greater than the secondthreshold TBW for the cache at the first time; and the controllerconfigured to cause the apparatus to modify the target ratio isconfigured to cause the apparatus to: increase a first target count forthe first mode for the at least one block of the second subset of blocksbased at least in part on the current TBW being greater than the secondthreshold TBW; and decrease a second target count for the second modefor the at least one block of the second subset of blocks based at leastin part on the current TBW being greater than the second threshold TBW.10. The apparatus of claim 7, wherein the comparing is performedaccording to a configured periodicity.
 11. The apparatus of claim 1,wherein the controller is further configured to cause the apparatus to:assign the first subset of blocks and the second subset of blocks to thecache based at least in part on a threshold capacity for the memorydevice.
 12. The apparatus of claim 1, wherein the controller is furtherconfigured to cause the apparatus to: assign blocks to the first subsetof blocks or the second subset of blocks based at least in part on athreshold total bytes written (TBW) for the cache.
 13. The apparatus ofclaim 1, wherein: the first block operating in the first mode storesfirst data in a single-level cell (SLC) and the second block operatingin the second mode stores second data in a multi-level cell (MLC), atri-level cell (TLC), or a quad-level cell (QLC); the first blockoperating in the first mode stores first data in an MLC and the secondblock operating in the second mode stores second data in a TLC or a QLC;or the first block operating in the first mode stores first data in aTLC and the second block operating in the second mode stores second datain a QLC.
 14. The apparatus of claim 1, wherein the memory devicecomprises a not-and memory device.
 15. A non-transitorycomputer-readable medium storing code comprising instructions which,when executed by a processor of an electronic device, cause theelectronic device to: configure a memory device with a cache comprisinga first subset of blocks configured to statically operate in a firstmode and a second subset of blocks configured to dynamically switchbetween operating in the first mode and a second mode, wherein a firstblock operating in the first mode is configured to store a firstquantity of bits per memory cell and a second block operating in thesecond mode is configured to store a second quantity of bits greaterthan the first quantity of bits per memory cell; store, for each blockof the second subset of blocks, a respective ratio of cycles performedin the first mode to cycles performed in the second mode; and select ablock from the second subset of blocks to switch from the first mode tothe second mode or from the second mode to the first mode responsive toa trigger and based at least in part on the respective ratio for theblock.
 16. The non-transitory computer-readable medium of claim 15,wherein the instructions, when executed by the processor of theelectronic device, further cause the electronic device to: assign, basedat least in part on a threshold total bytes written (TBW) for the cache,each block of the second subset of blocks a respective target ratio ofcycles performed in the first mode to cycles performed in the secondmode according to a respective first target count for the first mode anda respective second target count for the second mode.
 17. Thenon-transitory computer-readable medium of claim 16, wherein theinstructions, when executed by the processor of the electronic device,further cause the electronic device to: identify the trigger to switchthe block from the first mode to the second mode; and determine therespective ratio for the block is greater than the respective targetratio for the block based at least in part on identifying the trigger,wherein the block is selected based at least in part on the determining.18. The non-transitory computer-readable medium of claim 16, wherein theinstructions, when executed by the processor of the electronic device,further cause the electronic device to: identify the trigger to switchthe block from the second mode to the first mode; and determine therespective ratio for the block is less than the respective target ratiofor the block based at least in part on identifying the trigger, whereinthe block is selected based at least in part on the determining.
 19. Thenon-transitory computer-readable medium of claim 16, wherein theinstructions, when executed by the processor of the electronic device,further cause the electronic device to: compare a current TBW for thecache at a first time to a second threshold TBW for the cache at thefirst time, the second threshold TBW being based at least in part on thethreshold TBW for the cache and the first time; and modify a targetratio for at least one block of the second subset of blocks based atleast in part on the comparing.
 20. The non-transitory computer-readablemedium of claim 19, wherein: the current TBW for the cache is less thanthe second threshold TBW for the cache at the first time; and theinstructions causing the electronic device to modify the target ratio,when executed by the processor of the electronic device, cause theelectronic device to: decrease a first target count for the first modefor the at least one block of the second subset of blocks based at leastin part on the current TBW being less than the second threshold TBW; andincrease a second target count for the second mode for the at least oneblock of the second subset of blocks based at least in part on thecurrent TBW being less than the second threshold TBW.
 21. Thenon-transitory computer-readable medium of claim 19, wherein: thecurrent TBW for the cache is greater than the second threshold TBW forthe cache at the first time; and the instructions causing the electronicdevice to modify the target ratio, when executed by the processor of theelectronic device, cause the electronic device to: increase a firsttarget count for the first mode for the at least one block of the secondsubset of blocks based at least in part on the current TBW being greaterthan the second threshold TBW; and decrease a second target count forthe second mode for the at least one block of the second subset ofblocks based at least in part on the current TBW being greater than thesecond threshold TBW.
 22. The non-transitory computer-readable medium ofclaim 15, wherein the instructions, when executed by the processor ofthe electronic device, further cause the electronic device to: assignthe first subset of blocks and the second subset of blocks to the cachebased at least in part on a threshold capacity for the memory device.23. The non-transitory computer-readable medium of claim 15, wherein theinstructions, when executed by the processor of the electronic device,further cause the electronic device to: assign blocks to the firstsubset of blocks or the second subset of blocks based at least in parton a threshold total bytes written (TBW) for the cache.
 24. A methodperformed by a memory system, comprising: configuring a memory devicewith a cache comprising a first subset of blocks configured tostatically operate in a first mode and a second subset of blocksconfigured to dynamically switch between operating in the first mode anda second mode, wherein a first block operating in the first mode storesa first quantity of bits per memory cell and a second block operating inthe second mode stores a second quantity of bits greater than the firstquantity of bits per memory cell; storing, for each block of the secondsubset of blocks, a respective ratio of cycles performed in the firstmode to cycles performed in the second mode; and selecting a block fromthe second subset of blocks to switch from the first mode to the secondmode or from the second mode to the first mode responsive to a triggerand based at least in part on the respective ratio for the block. 25.The method of claim 24, further comprising: assigning, based at least inpart on a threshold total bytes written (TBW) for the cache, each blockof the second subset of blocks a respective target ratio of cyclesperformed in the first mode to cycles performed in the second modeaccording to a respective first target count for the first mode and arespective second target count for the second mode.